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August 23, 2011

Learning Lessons From Japan’s Fukushima Disaster

by editor

According to a new report from MIT, Japan's Fukushima disaster could provide valuable lessons for the design of future nuclear power plants.

The report said that emergency generators should be better protected from flooding and other extreme natural events. It also said that increasing the spacing between reactors at the same site would help prevent an incident at one reactor from damaging others nearby.

MIT's Department of Nuclear Science and Engineering (NSE) put out the report based on an analysis of how events unfolded at the troubled plant in the days and weeks following Japan's devastating earthquake and tsunami on March 13.

The report says that health risks to the public, and even to workers at the plant, have been negligible, despite the significant releases of radiation over the last few months.

“A lot of information that was not available when we started has become available,” Jacopo Buongiorno, the Carl Richard Soderberg Associate Professor of Power Engineering and lead author of the new report, said in a press release.

He said during the first days of the accident there were three critical delays that have not yet been well explained. The delays involved operating some safety-critical valves, injecting water into the reactor cores and venting the containment buildings.

“There was disruption and confusion around the site” during the crucial early hours, Buongiorno said in a press release. “Things that normally would take minutes, such as reading an instrument or connecting a cable or a hose, took hours” because of the lack of power and the debris and destruction. “Given the situation, they reacted as well as they could,” he says.

The report suggests that emergency backup generators should be well separated into at least two locations: one situated high up to protect against flooding, and the other down low to protect against hazards like airplane crashes.

It also says that future plants should increase the spacing between reactor buildings.

The researchers suggest that officials should be cautious about decisions to evacuate large areas around a damaged nuclear plant in cases where population has already been devastated by a natural disaster.

Buongiorno says at Fukushima, “ironically, the biggest [health] consequences may be from the prolonged evacuation."

The report emphasizes that all engineered structures have their own risks, especially when subjected to extreme conditions they were never designed to withstand.

“If you have an accident in your car, you don´t stop driving a car, you learn from it,” Buongiorno says. Continuing the analogy, “in this case, the accident was like a tree that fell on the car. It wasn´t the car itself.”

He said it may take years to fully learn from the lessons of this accident.

“It took 20 years to fully absorb the lessons of Three Mile Island,” he said in a statement. “Some of these questions are complex, requiring quantitative analysis to fully evaluate the data and make rational decisions about how best to respond.”